1. Field of the Invention
The present invention generally relates to a spark ignition internal combustion engine with direct fuel injection. More specifically, the present invention relates to a spark ignition internal combustion engine with direct fuel injection that achieves an improved combustibility of the fuel during stratified combustion.
2. Background Information
A spark ignition internal combustion engine with direct fuel injection is configured and arranged to perform a highly lean combustion by directly injecting a fuel into a cylinder from a fuel injection valve and forming a stratified air-fuel mixture in the cylinder during spark ignition combustion. Thus, with the direct fuel injection engine, the fuel consumption can be significantly reduced, particularly when the engine is operating under low and medium loads.
In order to steadily ignite and combust the air-fuel mixture in the direct fuel injection engine, it is critical to reliably form an air-fuel mixture mass in a stratified state in the cylinder, which has an appropriate size and appropriate air-fuel ratio according to the speed and load of the engine.
An appropriate stratified air-fuel mixture can be formed in the cylinder by providing a bowl-shaped cavity on a piston, setting a fuel stream injected from the fuel injection valve to collide against a wall surface of the bowl-shaped cavity, and forming a fuel stream circulation along the wall surface of the bowl-shaped cavity. For example, Japanese Laid-Open Patent Publication No. 11-82028 discloses a direct fuel injection spark ignition internal combustion engine that forms an appropriate stratified air-fuel mixture in a cylinder by disposing the fuel injection valve in the vicinity directly above the cavity, setting the fuel stream to collide against the cavity perimeter wall surface, and thereby forming a fuel stream circulation toward the center part of the cavity.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved spark ignition internal combustion engine with direct fuel injection. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.